Method and material for separating oil from oil-containing water

ABSTRACT

Oil is separated from oil-containing water by contacting the oil-containing water with an adsorbing material consisting mainly of atactic, noncrystalline polypropylene having a molecular weight of 10,000 to 100,000. Straw, wood wool, or natural fibers can be used as a carrier for the atactic-noncrystalline polypropylene.

United States Patent [21 1 Appl. No. [22] Filed [45] Patented Fukumotoand Aiko Nagao legal representative of Nobuo Nagao deceased to OsmanKgyo V Kabushiki Kaisha Tokyo, Japan [32] Priorities Nov. 6, 1967 [33]Japan 31 42/70928;

Apr. 27, 1968, Japan, No. 43/34244; May 2, 1968, Japan, No. 43/115413;July 12, 1968, Japan, No. 43/421470 [54] METHOD AND MATERIAL FORSEPARATING OIL FROM OIL-CONTAINING WATER 13 Claims, 4 Drawing Figs.

52 U.S.Cl 210/40, 210/242, 210/282, 210/484, 210/D1G. 21 [51] Int. ClE0211 75/04 By said OsIiima, said Kajiyama, said [50] Field of Search"2.: 210/36, 39, 40, 266, 282, 484, 502, 502, DIG. 21; 252/426, 428

[56] References Cited UNITED STATES PATENTS 2,063,086 12/1936 Fitzgerald210/282 2,361,092 10/1944 Gilbert et a1 210/502 X 2,367,384 1/1945TymStra et a1. 210/40 X 2,399,158 4/1946 Armaly 210/484 2,464,204 3/1949Baker.... 210/40 X 3,115,459 12/1963 Giesse 210/484 3,147,216 9/1964Oemler 210/40 3,198,731 8/1965 DeLew 210/42 3,252,270 5/1966 Pall etal... 210/505 X 3,334,042 8/1967 Teitsmaum 210/40 X 3,382,170 5/1968Pape 210/40 X 3,441,140 4/1969 Thurber 210/282 X 3,464,920 9/1969 Pirsonet a1. 210/36 X Primary Examiner-Samih N. Zaharna Anorney- Fred C.Philpitt ABSTRACT: Oil is separated from oil-containing water bycontacting the oil-containing water with an adsorbing materialconsisting mainly of atactic, noncrystalline polypropylene having amolecular weight of 10,000 to 100,000.

Straw, wood wool, or natural fibers can be used as a carrier for theatactic-noncrystalline polypropylene.

PATENTEDNUV 2 METHOD AND MATERIAL FOR SEPARATING OIL FROM OIL'CONTAININGWATER The present invention relates to a method and material forseparating oil from water, and more particularly to a method andmaterial for separating oil floating on water surface or being suspendedas colloidal particles in water, using an adsorbing material mainlyconsisting of noncrystalline, atactic polypropylene.

Removal of oil floating on water surface or suspended in water ascolloidal particles is very important for water treatment and preventionof public nuisance, and there have been heretofore proposed thefollowing methods:

l. A method based on coagulation of oil by a coagulant consisting mainlyof surface-active agent and successive collection of coagulated oilfloating on water surface.

2. A method based on emulsification and dispersion of oil by anemulsifying agent consisting mainly of detergent and kerosene.

3. A method based on adsorption of oil on a mixture of clay ordiatomaceous earth and a surface-active agent and successivesedimentation of oil-adsorbed clay or diatomaceous earth from watersurface, and

4. A method based on collection of oil using floatable material ofnatural fibers such as wheat straws as an adsorbing carrier.

However, these methods still have drawbacks and are not deemed effectiveones.

For example, the method (I) was developed in Germany some years ago, andas the coagulated oil is in a semifiuid state and thus it is necessaryto subject the collected coagulated oil to further oil-water separationand heating. Furthermore, it is a disadvantage to use a large amount ofexpensive coagulant.

The method (2) is based simply on the emulsification and dispersion, andthus oil is not removed from water essentially and consequently thereare cases that the quality of water becomes much worse. Further, theemulsifying agent itself is expensive and it is said that in case ofheavy oil treatment, the treating cost is about five times as expensiveas the cost of heavy oil treated. Furthennore, in some countriesregulations for prohibiting the use of such method are in force on theground of water quality deterioration. Thus, the method (2) is notpreferable.

The method (3) is based on the sedimentation, of oil-adsorbed clay ordiatomaceous earth and thus does not required so much labor in thetreatment, but the sedimented adsorbed oil cannot be recovered.

The method (4) is widely used in the world, but the adsorbing capacityof adsorbing carrier is small and consequently, a large amount of wheatstraws are necessary to use. The wheat straws rot when they are made wetor humid, and thus cannot be stored in open air in a high humid countrylike Japan: hence the procurement in emergency is difficult.Oil-adsorbed straws also adsorbs water, and the disposal of theoil-adsorbed straws is difficult after landing. The oil-adsorbed strawsare usually burned.

For sludge cleaning of oil tank of crude oil tanker, fuel oil tank ofship, or oil tank on land or cleaning for repair, it is necessary to usea large amount of surface-active agent and waste cloths, as well as muchlabor and time.

Furthermore, for the treatment of waste cleaning liquor including oilfrom the tanker or ship oil tank, it is necessary to employ a number ofbarges for carrying such waste cleaning water as well as a large scaleoil-water separator, and further heating is necessary for suchtreatment.

Accordingly, the cleaning operation becomes very expen- SIVC.

An object of the present invention is to provide a method and materialfor removing oil floating on water surface or being'suspended in waterin the form of colloidal particles.

Another object of the present invention is to provide a method andmaterial for considerably reducing costs required for separation of oiland water at the purification of various oil tanks as well as cleaningof oil.

ln the present invention, these objects can be attained by utilizingnoncrystalline, atactic polypropylene.

The present invention is to provide a method and material for removingoil from a mixture of water and oil, from water surface or fromoil-attached wall surface of a vessel, which comprises allowingnoncrystalline, atactic polypropylene having a molecular weight of10,000 to 100,000 surface-active agent-containing noncrystalline,atactic polypropylene, or noncrystalline, atactic polypropylene-coatedcarrier material such as wood wool, straws, natural fibers, to come incontact with said oil thereby to adsorb said oil on polypropylene. Themolecular weight, as referred to herein, means a mean molecular weightobtained by inserting an intrinsic viscosity [1;] as measured intetraline at l35 C. into the following equation:

The noncrystalline, atactic polypropylene used in the present inventionis a byproduct polypropylene having a molecular weight of from 10,000 to100,000 obtained when crystalline polypropylene is prepared, and has notbeen heretofore utilized in the industry and burned as a waste material.The noncrystalline, atactic polypropylene is separated from crystallinepolypropylene in a process for preparing crystalline polypropylene andobtained in a state where the noncrystalline polypropylene is dissolvedin an inert solvent for polymerization. in order to recover the inertsolvent from the noncrystalline polypropylene, the noncrystallinepolypropylene and inert solvent are to be separated. ln that case, thenoncrystalline polypropylene is obtained in a granular, or porousgranular or powdery state.

When the noncrystalline polypropylene is obtained in a lump state, suchlump is pulverized to a flaky or granular state. in one embodiment ofthe present invention, powdery, granular or flaky polypropylene ispreferably used. The amount of atactic polypropylene is 10 to percent byweight on the basis of weight of oil to be recovered, but depends uponthe species of oil. Thus, it is preferable to conduct a preliminary testto determine the amount of polypropylene to be added. Of course it isadvantageous to use atactic polypropylene in the form as porous aspossible. ln order to separate and remove oil floating on water surfaceor being mixed with water, the noncrystalline polypropylene is added towater in said state as it is or added to water together with such anassisting agent as surface-active agent.

The noncrystalline polypropylene is water-repellant but has an affinitytoward oil and thus well adsorbs oil. Thus, the object of adsorbing andcatching oil can be attained with a small amount of noncrystallinepolypropylene.

In another embodiment of the present invention, a noncrystalline,atactic polypropylene-coated material is used to separate and recoveroil from water surface. The carrier material for polypropylene is such amaterial having a lower apparent specific gravity than water such aswood wool, straws or natural fibers, and is coated with noncrystallinepolypropylene by dissolving noncrystalline polypropylene into a solventand applying the thus obtained solution to the surface of carriermaterial or by melting said polypropylene without using any solvent anddipping said carrier material into molten polypropylene.

According to the solvent method, it is possible to coat one part byweight of carrier material with about one to about three parts by weightpolypropylene and according to the melting method, it is possible tocoat one part by weight of carrier material with five to 10 parts byweight of polypropylene. The carrier material is thus uniformly coatedwith the noncrystalline, atactic polypropylene and has its originalshape on account of the rigidity of the carrier material itself. Thethus obtained adsorbing material has a large surface area.

When wood wool, straws or natural fibers are used singly, as anoil-adsorbing material, adsorption of oil is interrupted if theadsorbing material adsorbs water at first. Even if oil is adsorbedthereon at first, the adsorbed oil is released from the adsorbingmaterial by the successive absorption of water. Further, the specificgravity of the adsorbing material increases with the absorption of waterand thus the water-absorbed material gradually sinks below the watersurface and is settled.

The polypropylene-coated oil adsorbing material prepared according tothe present invention never releases oil, once the oil has been adsorbedthereon, and further as the carrier material is entirely v coated withwater-repellant atactic,

noncrystalline polypropylene, the adsorbing material will never absorbwater, thus never undergoes increase in specific gravity and can bealways kept floating on water surface.

In case of the wood wool, the polypropylene-coated wood wool has ahigher buoyancy than the single atactic, noncrystalline polypropylenehas, and can be kept floating on water surface for a longer period oftime. Further, the wood wool is prevented from decaying by suchpolypropylene coating.

The advantages of the present adsorbing material are enumerated asfollows:

I. Only oil is selectively adsorbed, and the atactic noncrystallinepolypropylene itself is water-repellant and thus the adsorbing materialis never made wet with water.

2. The atactic, noncrystalline polypropylene commercially available isordinarily porous or has an irregular surface, and thus the surface areais very large. Accordingly, the adsorbing effect upon oil of the presentadsorbing material is about 10 times as large as that of theconventionally used straw.

. Powdery atactic, noncrystalline polypropylene-adsorbing material has atrue density of 0.85 and bulk density of 0.1 to 0.3, and is convenientto handle owing to its light weight.

4. Collection of oil-adsorbed atactic, noncrystallinepolypropylene-adsorbing material in water can be simply made for exampleby a net because the present adsorbing material is a floatable solid.

5. Once oil is adsorbed on the present adsorbing material, adsorbed oilis hardly released therefrom by mere hand rubbing. Water retainedbetween clearances can be readily removed by draining off water afterthe collected adsorbing material has been stored in'a storing place orbag.

6. Oil-adsorbed atactic, noncrystalline polypropylene or material coatedtherewith can be burned as fuel as well as those which have not adsorbedoil (For example, a very good result can be obtained when atacticpolypropylene is utilized in limestone firing.

7. The atactic, noncrystalline polypropylene itself is produced as apetrochemical byproduct at a low cost and in a large amount. Further,its supply is very stable.

8. The atactic, noncrystalline polypropylene never undergoesdecomposition or deterioration in quality with time, and thus can bestored in an open air.

In order to effectively conduct removal of oil floating on water surfaceor being suspended in water as well as purify water, it is preferable touse a method for forcibly passing oilcontaminated water through a vesselpacked with said noncrystalline polypropylene-adsorbing material. Forexample, in treating a large amount of a mixture of water and oil, thatis, in separating oil contained in ballast water in a tanker, oil can beseparated in a very short period of time with minimum labor for forciblypassing oil-contaminated water through a cylindrical vessel packed withatactic, noncrystalline polypropylene-adsorbing material, by means of apump, while the adsorbing material is supported at both ends with wirenettings having a size of for example 10 mesh. In such a case, it hasbeen necessary in separating oil in a suspended state according to theconventional method, to use a large oilwater separator and apply heatthereto. n the other hand, the suspended oil can be cleanly separatedfrom water according to the present invention, and thus theoil-separated water can be discharged as it is, without any trouble.

Further, it has been difficult to remove oil from the oilsticked wallsurface of an empty oil tank, and it has been necessary to wipe out oilfrom the wall surface with a waste cloth. However, according to thepresent invention, oil can be removed from the wall surface by placingthe atactic,

noncrystalline polypropylene-adsorbing material in an empty oil tank,further adding a large amount of water thereto, and stirring water inthe tank. Such separation is based on the fact that the atactic,noncrystalline polypropylene-adsorbing material rubs the oil-stickedwall surface by the stirring as if the wall were wiped with a wastecloth, and consequently oil is released from the wall surface, and thereleased oil is adsorbed onto the atactic, noncrystallinepolypropylene-adsorbing material. Then, the solution mixture containingthe oil-adsorbed polypropylene-adsorbing material is withdrawn from thetank and passed through a wire netting, whereby only thepolypropylene-adsorbing material is collected on the wire netting. Inthat case, a layer of the collected polypropyleneadsorbing materialhelps further filtering operation as in the ordinary filteringoperation.

Any surface-active agent can be used as an assisting agent, but in thecase the surface active agent is added to the atactic, noncrystallinepolypropylene, it is preferable to use 0.5 to 20 percent by weight ofsurface-active agent on the basis of the atactic, noncrystallinepolypropylene.

In another preferable mode of removing oil floating on the water surfaceaccording to the present invention, granular, flaky, or lump atactic,noncrystalline polypropylene-adsorbing material packed in a bag knittedwith polyethylene or polypropylene threads or preferably with theirmonofilaments, are effectively employed as an oil fence element forcatching oil floating on water surface.

In other preferable mode of removing oil from water according to thepresent invention, granular, flaky or lamp atacticnoncrystalline-adsorbing material packed in a bag knitted withpolyethylene or polypropylene threads or preferably with theirmonofilaments, are efiective utilized as an oil separator, by insertinga perforated tube having a closed end into the bag to supplyoil-contaminated water.

These modes of operation are explained hereunder with reference to thedrawings:

FIG. 1 is a partly cutaway side view of an oil-fence element accordingto the present invention;

FIG. 2 is a cross-sectional view of the oil fence element of FIG. 1;

FIG. 3 is a partly cutaway side view of oil separator according to thepresent invention; and

FIG. 4 is a cross-sectional view of the oil separator of FIG. 3.

In FIGS. 1 and 2 a cylindrical bag I knitted with polyethylene orpolypropylene threads or monofilaments is packed with flaky atactic,noncrystalline polypropylene-adsorbing material 2 or a mixture of thesematerial and polyurethane foam. Both ends of the bag are closed with athread, thereby an oil fence element is built up. The thus built-up oilfence elements are connected with one another in series to form an oilfence. The present oil fence can keep a stable floating state on watersurface and can be used in a straight form, curved form or loop form,depending upon the situation in preventing floating oil on water surfacefrom flowing away or in collecting floating oil in the inside of theloop made by the fence. As the present oil fence consists of nettingsand adsorbing material packings having clearances, water can be freelypassed and thus the present oil fence is never turned around by thewaves. As a result oil floating on water surface can never pass over thepresent oil fence. On the contrary, when water-containing oil passesthrough the present oil fence, only oil is adsorbed on the oil fence.Excess unadsorbed oil is retained by the fence, and the retained oil isfurther adsorbed on the powdery, granular, flaky or lamp atactic,noncrystalline polypropylene adsorbing material by spraying the sameover said retained oil, or by passing the retained oil through thepresent oil separator shown in FIGS. 3 and 4.

In FIGS. 3 and 4, a cylindrical bag 1 knitted with polyethylene orpolypropylene thread, or monofilaments is packed with flaky atactic,noncrystalline polypropylene-adsorbing material 2. A perforated pipe 4having one closed end is inserted into the cylindrical bag along thecenterline of the cylindrical bag so that the closed end may be withinthe bag. The other open end outside the bag is connected to a pipe forsupplying an oil-containing water. The entire bag is allowed to float onwater surface. By supplying the oil-containing water to the perforatedpipe 4, the oilcontaining water is injected through perforations 5 intothe inside of the bag. Only oil is adsorbed and caught by packings ofthe flaky atactic, noncrystalline polypropylene-adsorbing material, andwater leaks through the clearances between packings to the outside ofthe bag. Water can pass through the packing clearances and surroundingnettings with less resistance.

The present oil separator can be conveniently and efficiently utilizedin combination with said oil fence. The advantages of the present oilseparator are enumerated below:

1. Lightweight and floatable on water. Thus, oil separation can beeffected on water surface.

2. Readily assemblable at working site.

3. No trouble with vigorous handling as well as contamination.

4. A large volume of water is treatable because of less resistance.

5. Structural material itself is cheap.

6. Nether heat nor power except that for pumping is required.

7. Saturated packing can be thrown away together with netting after onlypipe is disengaged.

The present invention is explained hereunder with reference to examples:

EXAMPLE 1 Five hundred kilograms of atactic, noncrystallinepolypropylene granules having sizes of 1 to 3 mm. and its aggregate wassprayed in a dockyard (depth of water: 8 m.; length: l50 m.; and width:100 m.) in which about 1,000 L of C heavy oil locally floated on watersurface, and the sprayed adsorbing material was collected at oneposition using a net with floats and transferred onto land by a crave.Cleaning was thereby completed. Man-hour required for that treatment was8 man-days.

For the same treatment, 150 drums of dispersing agent (2,500 per drum)were used to ernulsify the floating oil. The man-hour required for thattreatment was 60 man-days.

It was found that the cleaning based on the present method was morecomplete than, that based on the conventional method, and further thatconsiderable saving in man-hour could be attained, as stated above.

EXAMPLE 2 ln sludge-removing work tank having a capacity of 5,000 tons,placed on land and used for B heavy oil, tons of atactic, noncrystallinepolypropylene granules were added to 80 tons of residual sludge percentoil and 80 percent sludge water), and further 100 tons of water wasadded thereto. After oil was adsorbed on said adsorbing material, waterwas drained off the adsorbing material, using a bag. The filtrate watercould be discharged to the ordinary drain pit (no oil was contained infiltrate water). The man-hour required therefor was 4 man-days, andfinishing with waste cloths was not necessary.

In the conventional method, about 40 man-days were required, and thedischarged water could not be thrown away through the ordinary drain pitwithout further oil separation from the discharged water.

EXAMPLE 3 For cleaning of a light oil tank having a volume of 100 in(one section: 5 m) at ship bottom, about 10 tons of atactic,noncrystalline polypropylene granules and 80 m of sea water were addedto the tank. The man-hour required for that work was l0 mun-days. In theconventional method, about 40 manduys were required. Further, the workcould not be started for 2 days after manholes were opened for ventinggas from the light oil in the conventional method. Such preparatoryperiod was not necessary at all in the present method. No sticked oilwas found on wall surface, and workers did not get dirty and no wastecloths were used at all. Thus, a remarkable cleaning effect could beattained.

EXAMPLE 4 in treating ballast water of a 50,000 ton ship, a cylindricalfilter (1.5 m. I X6 m.) was used. About 3 tons of atactic,noncrystalline polypropylene powders was added to 9.3 m. of ballastwater containing about 1 percent of oil. and water was pumped to saidfilter and forcibly passed therethrough. Oil content of discharged waterreduced to 20 p.p.m.

EXAMPLE 5 Wood wool was dipped in a solution consisting of 30 parts byweight of atactic polypropylene having a molecular weight of 15,000 and70 parts by weight of toluene at 50 C., and taken out therefrom. Then,toluene was removed by evaporation, whereby a polypropylene-coated woodwool consisting of one part by weight of wood wool and about one tothree parts by weight of atactic polypropylene was obtained. The thusobtained adsorbing material had a very remarkable adsorption effect uponfloating oil. That is, about one to three parts by weight of oil wasadsorbed on one part by weight of adsorbing material. No release of oilfrom the adsorbing material by water was observed at all.

EXAMPLE 6 Wood wool was dipped in molten atactic polypropylene having amolecular weight of 10,000 at C. and taken out therefrom and air-cooled,whereby propylene-coated wood wool consisting of one part by weight ofwood wool and five to 10 parts by weight of atactic polypropylene wasobtained, while keeping the original wood wool clearances.

In the adsorbing material prepared by such melting method, only aboutone part by weight of oil was instantly adsorbed on one part by weightof adsorbing material, but the swelling layer was so thick afteradsorption that the adsorbing effect was more durable than that based onthe solvent method. After 3 hours, the amount of oil adsorption reachedfive to 10 parts by weight per one part by weight of adsorbing material.

When the wood wool was to be coated with atactic polypropylene accordingto the melting method, it was found that the wood wool was charred at atemperature above 220 C., and it is necessary that the temperature ofwood wool be below 220 C. even locally.

EXAMPLE 7 A 40-cm. 1 cylindrical bag knitted with polyethylenemonofilaments of 400 denier was packed with atactic, noncrystallineporous polypropylene flakes having sizes of 20 to 30 mm., and both endsof the bag was closed with threads, whereby an oil fence element wasobtained. Oil fence consisting a plurality of the oil fence elements andhaving a length of about 5 m. was immersed in a drain pit through whichwatercontaining oil was flowing, and used as an oil fence. Further, afence having a length of 20 m. was placed in a semicircular state at aplace where waste water was discharged to sea. In both cases, goodresults were obtained. When the waste sea water having 0.5 to 1 percentof oil dispersed on water surface was treated in said fence, the oilcontent was reduced to 10 ppm.

EXAMPLE 8 A cylindrical bag knitted with polyethylene monofilamentshaving 400 denier (bag diameter: 60 cm.; length: 5 m.) was packed withatactic, noncrystalline polypropylene flakes having sizes of 20 to 30mm., and then a perforated polyvinyl chloride pipe having a closed end,a diameter of 4 inches, and about 300 perforations having a size of lmm. was inserted along the centerline of bag so that the closed end ofpipe may be located within the bag. To other end of the pipe wasconnected to a waste water pipe, and the entire bag was floated on watersurface. One hundred Tons per hour of Ballast water containing 800p.p.m. of oil was passed through said oil separator, whereby watercontaining p.p.m. of oil was obtained.

We claim:

l. A method for separating oil from water-containing oil, whichcomprises contacting oil-containing water with an adsorbing material.consisting mainly of atactic, noncrystalline polypropylene having amolecular weight of 10,000 to 100,000 and thereby adsorbing only oilonto the adsorbing material.

2. A method according to claim 1, wherein the adsorbing material ispowdery, flaky, granular or lump atactic, noncrystalline polypropylene.

3. A method according to claim I, wherein the adsorbing material is usedin the presence of a surface-active agent.

4. A method according to claim 1, wherein the adsorbing materialconsists of atactic, noncrystalline polypropylenecoated wood wool,straws or natural fibers.

5. A method according to claim 1, wherein the adsorbing materialconsists of a bag packed with packings consisting 8. A method accordingto claim 1 wherein the adsorbing material is a mixture of powdery,flaky, granular or lump of atactic, noncrystalline polypropylene andpolyurethane foam.

9. An oil-adsorbing material for separating oil from oil-containingwater which comprises wood wools, straws or natural fibers as a carrierand atactic, noncrystalline polypropylene having a molecular weight of[0,000 to 100,000, said wood wools, straws or natural fibers beingcoated with said polypropylene.

10. An oil-adsorbing structure for separating oil from oilcontainingwater which comprises a bag and packing consisting mainly of atactic,noncrystalline polypropylene and wherein said bag is provided with aperforated tube for introducing oil-containing water, having one closedend and one opened end, the closed end being located in the inside ofthe bag and the open end being located at the outside of the bag andconnected to an oil-containing water feeding source.

11. An oil-adsorbing structure according to claim 10 wherein the bag isknittings of polyethylene or polypropylene threads or monofilaments.

12. A fence for collecting oil which is floating on water surface whichcomprises a plurality of fence elements which comprise netlike elongatedbags containing buoyant-packed materials consisting mainly of atactic,noncrystalline polypropylene; each of said elements having clearances sothat water can be freely passed therethrough and being connected withone another to form said fence which is capable of catching oil floatingon a water surface, and which is capable of keeping a stable floatingstate on water surface.

13. An oil-adsorbing structure according to claim 12 wherein the bag isknittings of polyethylene or polypropylene threads or monofilaments.

2. A method according to claim 1, wherein the adsorbing material ispowdery, flaky, granular or lump atactic, noncrystalline polypropylene.3. A method according to claim 1, wherein the adsorbing material is usedin the presence of a surface-active agent.
 4. A method according toclaim 1, wherein the adsorbing material consists of atactic,noncrystalline polypropylene-coated wood wool, straws or natural fibers.5. A method according to claim 1, wherein the adsorbing materialconsists of a bag packed with packings consisting mainly of atactic,noncrystalline polypropylene.
 6. A method according to claim 5, whereinthe bag is knittings of polyethylene or polypropylene threads ormonofilaments.
 7. A method according to claim 5, wherein the adsorbingmaterial has a means for feeding the oil-containing water into the bagand oil is adsorbed on packings consisting mainly of atactic,noncrystalline polypropylene while the oil-containing water passes fromsaid feeding means through said packing outwards.
 8. A method accordingto claim 1 wherein the adsorbing material is a mixture of powdery,flaky, granular or lump of atactic, noncrystalline polypropylene andpolyurethane foam.
 9. An oil-adsorbing material for separating oil fromoil-contAining water which comprises wood wools, straws or naturalfibers as a carrier and atactic, noncrystalline polypropylene having amolecular weight of 10,000 to 100,000, said wood wools, straws ornatural fibers being coated with said polypropylene.
 10. Anoil-adsorbing structure for separating oil from oil-containing waterwhich comprises a bag and packing consisting mainly of atactic,noncrystalline polypropylene and wherein said bag is provided with aperforated tube for introducing oil-containing water, having one closedend and one opened end, the closed end being located in the inside ofthe bag and the open end being located at the outside of the bag andconnected to an oil-containing water feeding source.
 11. Anoil-adsorbing structure according to claim 10 wherein the bag isknittings of polyethylene or polypropylene threads or monofilaments. 12.A fence for collecting oil which is floating on water surface whichcomprises a plurality of fence elements which comprise netlike elongatedbags containing buoyant-packed materials consisting mainly of atactic,noncrystalline polypropylene; each of said elements having clearances sothat water can be freely passed therethrough and being connected withone another to form said fence which is capable of catching oil floatingon a water surface, and which is capable of keeping a stable floatingstate on water surface.
 13. An oil-adsorbing structure according toclaim 12 wherein the bag is knittings of polyethylene or polypropylenethreads or monofilaments.